Image pickup apparatus

ABSTRACT

A first control unit ( 172 ), which controls the timing at which a first image pickup unit ( 110 ) starts exposure, obtains a second difference (Δt 2 ) by subtracting a first difference (Δt 1 ) from an exposure-output time (AA) of the first image pickup unit ( 110 ), and outputs a first control signal (CTR 1 ) for delaying the timing at which the first image pickup unit ( 110 ) starts an exposure, by the second difference (Δt 2 ). The exposure-output time is a time lag between when the image pickup unit starts an exposure and when output of an image signal obtained by the exposure is started. The first difference (Δt 1 ) is a difference between a timing at which the first image pickup unit ( 110 ) started outputting a predetermined image signal and a timing at which a second image pickup unit ( 150 ) started an exposure for obtaining an image signal that the second image pickup unit ( 150 ) outputted immediately after the first image pickup unit ( 110 ) started outputting the predetermined image signal. In such a way, the timings at which a plurality of image pickup units provided in an image pickup apparatus start exposure are synchronized.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. application Ser. No.14/001,540, filed Aug. 26, 2013, which is a national stage entry ofPCT/JP2012/001280, filed Feb. 24, 2012, claiming priority based onJapanese Patent Application No. 2011-050114, filed Mar. 8, 2011, thedisclosures of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to an image pickup apparatus and morespecifically to an image pickup apparatus including a plurality of imagepickup units.

BACKGROUND ART

Imaging of a subject from a plurality of different viewpoints is beingperformed in various technological fields. Examples include stereocameras, which images a subject from left-eye and right-eye viewpointsand generate a three-dimensional picture from the left-eye-viewpoint andright-eye-viewpoint images, and twin-lens stereoscopic, electronic,three-dimensional image pickup apparatuses. The “twin-lens stereoscopic”refers to a technology for measuring the position or the like of amobile object, such as a vehicle, robot, or animal, and is a techniqueby which such as the distance from the image pickup apparatus to themobile object is obtained from a picture obtained by imaging the mobileobject from different angles using a plurality of image pickup unitsincluded in the image pickup apparatus and from a parameter, such as thefocal length of the lens of each image pickup unit or the distancebetween the image pickup units, according to the principle oftriangulation.

Image pickup apparatuses as described above are required to synchronizethe timings at which the image pickup units start exposures. Forexample, in an image pickup apparatus disclosed in Patent Literature 1,as shown in FIG. 10, a sensor drive signal generation unit 34 generatesa sensor drive signal and outputs it to a first CCD image pickup unit 12and a second CCD image pickup unit 22 to cause the two image pickupunits to perform exposures simultaneously. Note that FIG. 10 isgenerated by changing the reference signs of FIG. 1 of Patent Literature1.

An image pickup apparatus disclosed in Patent Literature 2 alsosynchronizes the timings at which two image pickup units startexposures, by providing an exposure start timing signal provided to oneimage pickup unit, as well as to the other image pickup unit.

In the following description, a control signal for causing an imagepickup unit to start an exposure, such as the sensor drive signal orexposure start timing signal, will be referred to as an exposure startsignal.

CITATION LIST Patent Literature

-   [Patent Literature 1] Japanese Unexamined Patent Application    Publication No. 2007-28236-   [Patent Literature 2] Japanese Unexamined Patent Application    Publication No. 2000-341719

SUMMARY OF INVENTION Technical Problem

If a plurality of image pickup units included in an image pickupapparatus receive the same exposure start signal, the image pickup unitsmay be able to start exposures simultaneously after the same length oftime.

However, the plurality of image pickup units included in the singleimage pickup apparatus are not necessarily the same image pickup units.For example, to reduce cost, high-functionality and low-functionalityimage pickup units may be used as one and the other image pickup units.Further, chips manufactured by different manufacturers may be used aschips corresponding to the plurality of image pickup units used in thesingle image pickup apparatus.

In these cases, the time taken from the reception of an exposure startsignal to the start of an exposure most likely varies between the imagepickup units. For this reason, even if the plurality of image pickupunits receive the same exposure start signal, they may start exposuresat different timings.

Solution to Problem

A first exemplary aspect of the present invention is a image pickupapparatus. The image pickup apparatus includes a first image pickupunit, a second image pickup unit, and a first control unit.

The first image pickup unit repeats an exposure and output of an imagesignal obtained through the exposure to obtain a first picture signaland outputs the first picture signal.

The second image pickup unit repeats an exposure and output of an imagesignal obtained through the exposure to obtain a second picture signaland outputs the second picture signal.

The first control unit controls the timing at which the first imagepickup unit or the second image pickup unit starts an exposure. Inparticular, in the case of controlling the timing at which the secondimage pickup unit starts an exposure, the first control unit subtracts afirst difference from exposure-output time of the first image pickupunit to obtain a second difference, and outputs a first control signalfor delaying the timing at which the second image pickup unit starts anexposure, by a value obtained by subtracting the second difference froman exposure interval. In the case of controlling the timing at which thefirst image pickup unit starts an exposure, the first control unitoutputs a first control signal for delaying the timing at which thefirst image pickup unit starts an exposure, by the second difference.

The exposure-output time is a time lag between when each of the firstand second image pickup units starts an exposure and when the imagepickup unit starts outputting an image signal obtained through theexposure.

The first difference is a difference between the timing at which thefirst image pickup unit started outputting a predetermined image signaland the timing at which the second image pickup unit started an exposurefor obtaining an image signal that the second image pickup unitoutputted immediately after the first image pickup unit startedoutputting the predetermined image signal.

The implementation of the image pickup apparatus according to the aboveexemplary aspect as any of a method and a system are also effective asother aspects of the present invention.

Advantageous Effects of Invention

According to the technology of the present invention, even if aplurality of image pickup units included in an image pickup apparatushave different functionalities, it is possible to synchronize thetimings at which they start exposures.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing an image pickup apparatus according to afirst embodiment of the present invention.

FIG. 2 is a diagram showing an example of the timings of signals in theimage pickup apparatus shown in FIG. 1 in a case in which a firstcontrol unit does not perform control.

FIG. 3 is a diagram showing an example of the timings of the signals inthe image pickup apparatus shown in FIG. 1 in a case in which the firstcontrol unit performs control.

FIG. 4 is a diagram showing an image pickup apparatus according to asecond embodiment of the present invention.

FIG. 5 is a diagram showing an example of the timings of signals in theimage pickup apparatus shown in FIG. 4.

FIG. 6 is a diagram showing an image pickup apparatus according to athird embodiment of the present invention.

FIG. 7 is a diagram showing an example of the timings of signals in theimage pickup apparatus shown in FIG. 6 in a case in which none of firstand second control units of a second image pickup unit performs control.

FIG. 8 is a diagram showing an example of the timings of the signals inthe image pickup apparatus shown in FIG. 6 in a case in which the firstcontrol unit of the second image pickup unit performs control and inwhich the second control unit thereof does not perform control.

FIG. 9 is a diagram showing an example of the timings of the signals inthe image pickup apparatus shown in FIG. 6 in a case in which both thefirst and second control units of the second image pickup unit performcontrol; and

FIG. 10 is a diagram showing a related-art example.

DESCRIPTION OF EMBODIMENTS

Now, embodiments of the present invention will be described withreference to the drawings. For the sake of clarity, the descriptionbelow and the drawings are subjected to omissions and simplification asappropriate. In the drawings, the same components are given the samereference signs and therefore repeated description thereof will beomitted as appropriate.

First Embodiment

FIG. 1 shows an image pickup apparatus 100 according to a firstembodiment of the present invention. The image pickup apparatus 100includes a first image pickup unit 110, a second image pickup unit 150,and a display unit 190. The first image pickup unit 110 and the secondimage pickup unit 150 receive the same exposure start signal ST. Theexposure start signal ST is outputted, for example, by depressing animaging start button (not shown) provided on the image pickup apparatus100.

Upon receipt of the exposure start signal ST, the first image pickupunit 110 starts imaging and thus obtains a first picture signal VA, andoutputs it to the display unit 190.

Upon receipt of the exposure start signal ST, the second image pickupunit 150 starts imaging and obtains a second picture signal VB throughthe imaging, and outputs the second image signal VB to the display unit190.

Using the first picture signal VA outputted from the first image pickupunit 110 and the second picture signal VB outputted from the secondimage pickup unit 150, the display unit 190 generates and displays athree-dimensional picture.

The first image pickup unit 110 and the second image pickup unit 150will be described in detail.

The first image pickup unit 110 includes an image sensor module 120 andan analysis unit 130. In response to the exposure start signal ST, thefirst image pickup unit 110 starts the first exposure and obtains animage signal A21 through the first exposure, and outputs it.Subsequently, the first image pickup unit 110 repeats an exposure andoutput of an image signal obtained through the exposure. In this way,the first image pickup unit 110 outputs sequentially image signals (A21,A22, etc.) forming the first picture signal VA to the display unit 190.

The time between when the first image pickup unit 110 starts an exposureand when it outputs an image signal obtained through the exposure (A21,A22, etc.) is referred to as “exposure-output time.” The“exposure-output time” varies according to a specification, such as aprocess performed in the image pickup unit, and therefore may varybetween the image pickup units. Hereafter, the exposure-output time ofthe first image pickup unit 110 will be represented by “AA.”

The image sensor module 120 is similar to a typical type of image sensormodule and includes a lens 122, an imaging element 124, and anadjustment unit 126. After the exposure starts, the imaging element 124sequentially photoelectrically converts optical signals from the lens122 into a plurality of image signals A11, A12, etc. at a predeterminedsampling rate (exposure rate) and outputs the image signals to theadjustment unit 126.

The adjustment unit 126 adjusts the gain of the image signals A11, A12,etc. from the imaging element 124 and outputs resulting image signalsA21, A22, etc. to the analysis unit 130.

The analysis unit 130 performs analysis by performing image processingon the image signals A21, A22, etc. from the image sensor module 120 andfeeds back exposure information FA corresponding to an analysis result,to the image sensor module 120. The analysis unit 130 also sequentiallyoutputs the image signals A21, A22, etc. together with a synchronizationsignal SA to the display unit 190.

The exposure information FA fed back to the image sensor module 120 bythe analysis unit 130 includes information, such as shutter speed orgain, and is used, for example, to control an exposure so that imagingcan be performed with optimum luminance. This function of the analysisunit 130 is called “auto exposure” and provided in a typical type ofimage pickup unit.

The second image pickup unit 150 includes an image sensor module 160 andan analysis unit 170. The image sensor module 160 includes a lens 162,an imaging element 164, and an adjustment unit 166.

The function blocks of the second image pickup unit 150 performoperations similar to those of the corresponding function blocks of thefirst image pickup unit 110 except that the analysis unit 170 differsfrom the analysis unit 130 of the first image pickup unit 110 and thatthe second image pickup unit 150 receives the synchronization signal SAthat the first image pickup unit 110 outputs at which outputting thefirst picture signal VA. Specifically, the second image pickup unit 150starts the first exposure in response to the exposure start signal STand outputs an image signal B21 obtained through the first exposure.Subsequently, the second image pickup unit 150 repeats an exposure andoutput of an image signal obtained through the exposure. In this way,the second image pickup unit 150 sequentially outputs image signals(B21, B22, etc.) forming the second picture signal VB to the displayunit 190. The second image pickup unit 150 outputs a synchronizationsignal SB along with the picture signals B21, B22, etc.

The first image pickup unit 110 and the second image pickup unit 150have the same exposure rate (sampling rate). Similarly, the firstpicture signal VA and the second picture signal VB have the same framerate. In the present embodiment, it is assumed that the exposure-outputtime of the second image pickup unit 150 (hereafter referred to as AB)is similar to the exposure-output time of the first image pickup unit110, AA.

The analysis unit 170 includes a first control unit 172. Except for thefunction of the first control unit 172, the analysis unit 170 performsan operation similar to that of a typical type of image pickup unit.Specifically, the analysis unit 170 performs analysis by performingimage processing on the picture signals B21, B22, etc. from the imagesensor module 160 and feeds back exposure information FB to the imagesensor module 160. It also sequentially outputs the image signals B21,B22, etc. to the display unit 190 in accordance with the synchronizationsignal SB. As with the exposure information FA, the exposure informationFB fed back to the image sensor module 160 by the analysis unit 170 isinformation for controlling an exposure so that imaging can be performedwith optimum luminance, such as shutter speed or gain for “autoexposure.”

In the present embodiment, the analysis unit 170 also incorporatesinformation indicating the amount by which the exposure start timingshould be delayed, into the exposure information FB in accordance with afirst control signal CTR1 discussed below and outputs the resultingexposure information FB to the image sensor module 160. Note that whenthe first control signal CTR1 indicates a value “0,” the analysis unit170 performs an operation similar to that of an analysis unit includedin a typical type of image pickup unit.

The first control unit 172 will be described in detail. First, referringto FIG. 2, a first difference Δt1 and a second difference Δt2 used inthe following description will be described. Note that FIG. 2 is anexample in which the first control unit 172 does not perform control.

The upper part of FIG. 2 shows an example of the timing relationshipamong the exposure start signal ST, exposures performed by the imagesensor module 120, capture of the image signals (image signals A21, A22,etc.) and image processing for analysis by the analysis unit 130, andthe synchronization signal SA in the first image pickup unit 110. Eachparallelogram below the exposure start signal ST represents a singleexposure; the upper-left vertex thereof represents the timing at whichthe exposure starts; and the lower-right vertex thereof represents thetiming at which the exposure completes. Each hexagon represents a singletime of capture by the analysis unit 130; the left vertex thereofrepresents the timing at which the capture starts; and the right vertexthereof represents the timing at which the capture completes. Eachrectangle represents a single time of image processing performed by theanalysis unit 130; the left side thereof represents the timing at whichthe image processing starts; and the right side thereof represents thetiming at which the image processing completes. The numbers in thediagram represent the chronological order. For example, the analysisunit 130 receives an image signal obtained through the first exposure atthe first capture, performs the first image processing on the imagesignal, and outputs the resulting image signal in synchronization with apulse indicated by “1” of the synchronization signal SA.

The interval between two consecutive exposures performed by the firstimage pickup unit 110 (hereafter referred to as exposure interval) isrepresented by “T.”

The lower part of FIG. 2 shows an example of the timing relationshipamong the exposure start signal ST, exposures performed by the imagesensor module 160, capture of the image signals (image signals B21, B22,etc.) and image processing for analysis by the analysis unit 170, andthe synchronization signal SB in the second image pickup unit 150. Themeanings of the figures, such as the parallelograms, hexagons, andrectangles, and the numbers are as described above. Since the firstimage pickup unit 110 and the second image pickup unit 150 have the sameexposure rate, the exposure interval of the second image pickup unit 150is also “T.”

As used in the present specification, the first difference Δt1 refers tothe difference between the timing at which the image pickup apparatus100 starts outputting a predetermined image signal and the timing atwhich the second image pickup unit 150 starts an exposure for obtainingan image signal that the second image pickup unit 150 outputsimmediately after the first image pickup unit 110 starts outputting thepredetermined image signal.

In the present embodiment, the first image signal is used as the“predetermined image signal.” That is, in the present embodiment, thefirst difference Δt1 refers to the difference between the timing atwhich the first image pickup unit 110 starts outputting the first imagesignal and the timing at which the second image pickup unit 150 startsan exposure for obtaining an image signal that the second image pickupunit 150 outputs immediately after the first image pickup unit 110outputs the first image signal.

In the example shown in FIG. 2, the image signal that the second imagepickup unit 150 starts outputting immediately after the first imagepickup unit 110 outputs the first image signal (image signal A21) isalso the first image signal (image signal B21). Accordingly, the firstdifference Δt1 is the difference between the timing at which output ofthe image signal A21 is started and the timing at which the exposure forobtaining the image signal B21 is started.

As described above, in the present embodiment, the synchronizationsignal SA is also inputted to the second image pickup unit 150. In thesecond image pickup unit 150, the first control unit 172 of the analysisunit 170 obtains the timing at which the first image pickup unit 110starts outputting the first image signal (image signal A21), on thebasis of the synchronization signal SA and then calculates thedifference between the timing obtained and the timing at which thesecond image pickup unit 150 starts an exposure for obtaining the firstimage signal (image signal B21). Thus, the first control unit 172obtains the first difference Δt1.

The first control unit 172 then subtracts the first difference Δt1 fromthe exposure-output time ΔA of the first image pickup unit 110 to obtainthe difference Δt2 and further subtracts the second difference Δt2 fromthe exposure interval T to obtain a value “T−Δt2.” The value “T−Δt2”serves as the first control signal CTR1 indicating the amount by whichthe second image pickup unit 150 should delay the timing at which itstarts the subsequent exposure. Note that in the present embodiment, thefirst control unit 172 previously holds the value of the exposure-outputtime AA of the first image pickup unit 110.

The analysis unit 130 of the first image pickup unit 110 incorporatesthe amount of delay (“T−Δt2”) indicated by the first control signal CTR1into the exposure information FB and feeds back the resulting exposureinformation FB to the image sensor module 160.

Since the image sensor module 160 has already started the secondexposure when the first control unit 172 obtains the first controlsignal CTR1 indicating the value “T−Δt2,” the image sensor module 160delays the third exposure.

Thus, FIG. 2 becomes a timing chart as shown in FIG. 3. Since the imagesensor module 160 delays the start of the third exposure by “T−Δ2,” thestart timings of the third and later exposures (third, fourth, etc.) bythe second image pickup unit 150 are the same as the start timings ofthe fourth and later exposures (fourth, fifth, etc.) by the first imagepickup unit 110, respectively.

As described above, in the present embodiment, the exposure-output timeΔA of the first image pickup unit 110 is equal to the exposure-outputtime ΔB of the second image pickup unit 150. Accordingly, if the starttiming of the fourth exposure by the first image pickup unit 110 is thesame as the start timing of the third exposure by the second imagepickup unit 150, the fourth image signal obtained by the first imagepickup unit 110 and the third image signal obtained by the second imagepickup unit 150 are outputted at the same timing. The same applies toimage signals obtained through later exposures.

As seen above, the image pickup apparatus 100 according to the presentembodiment can synchronize the timings at which the two image pickupunits start exposures.

Further, if the two image pickup units have the same exposure-outputtime, the timings at which the two image pickup units output imagesignals are synchronized.

Second Embodiment

The image pickup apparatus 100 according to the first embodimentsynchronizes the timings at which the first image pickup unit 110 andthe second image pickup unit 150 start exposures, by delaying the timingat which the second image pickup unit 150 starts an exposure, by“T−Δt2.” Alternatively, the timings at which the first image pickup unit110 and the second image pickup unit 150 start exposures may besynchronized by delaying the timing at which the first image pickup unit110 starts an exposure. This will be described using an image pickupapparatus 200 according to a second embodiment shown in FIG. 4.

The image pickup apparatus 200 shown in FIG. 4 is similar to the imagepickup apparatus 100 shown in FIG. 1 except that analysis units 132 and174 included in the first image pickup unit 110 and the second imagepickup unit 150 differ from the analysis units 130 and 170 shown in FIG.1, respectively.

In the present embodiment, the analysis unit 132 receives the firstcontrol signal CTR1 from the second image pickup unit 150, specifically,from the analysis unit 174 of the analysis unit 170. The analysis unit132 incorporates information indicating the amount by which the exposurestart timing should be delayed, into the exposure information FA inaccordance with the first control signal CTR1 and outputs the resultingexposure information FA to the image sensor module 120. Note that whenthe first control signal CTR1 indicates a value “0,” the analysis unit132 operates as an analysis unit included in a typical type of imagepickup unit operates.

A first control unit 176 included in the analysis unit 174 of the secondimage pickup unit 150 outputs the first control signal CTR1 to theanalysis unit 132 of the first image pickup unit 110. This first controlsignal CTR1 differs from the first control signal CTR1 in the firstimage pickup unit 110. Further, the exposure information FB fed back tothe image sensor module 160 by the analysis unit 174 does not includeinformation on the first control signal CTR1.

Hereafter, the first control signal CTR1 outputted by the first controlunit 176 of the analysis unit 174 will be described. It is assumed thatwhere the first control unit 176 does not perform control, the timingsof the signals are similar to those in the example shown in FIG. 2.

In the present embodiment, the first control unit 176 previously holdsthe value of the exposure-output time ΔA of the first image pickup unit110 and subtracts the first difference Δt1 from the exposure-output timeΔA to obtain the difference Δt2. The first control unit 176 then outputsthe difference Δt2 to the analysis unit 132 of the first image pickupunit 110.

The analysis unit 130 of the first image pickup unit 110 incorporatesthe amount of delay (in this case, the difference Δt2) indicated by thefirst control signal CTR1 into the exposure information FA and feedsback the resulting exposure information FA back to the image sensormodule 120.

Since the first image pickup unit 110 has already started the secondexposure when the first control unit 176 obtains the first controlsignal CTR1 indicating the difference Δt2, the first image pickup unit110 delays the third exposure.

Thus, FIG. 2 becomes a timing chart as shown in FIG. 5. Since the imagesensor module 120 delays the start of the third exposure by thedifference Δt2, the start timings of the third and later exposures(third, fourth, etc.) by the first image pickup unit 110 are the same asthe start timings of the third and later exposures (third, fourth, etc.)by the second image pickup unit 150, respectively.

The exposure-output time ΔA of the first image pickup unit 110 is equalto the exposure-output time ΔB of the second image pickup unit 150.Accordingly, if the first image pickup unit 110 and the second imagepickup unit 150 start the respective third and later exposures at thesame timings, these image pickup units output the respective third andlater image signals at the same timings.

As seen above, the image pickup apparatus 200 according to the presentembodiment can produce effects similar to those of the image pickupapparatus 100 according to the first embodiment.

Third Embodiment

To perform imaging using two image pickup units and obtain a correctthree-dimensional picture, it is necessary to synchronize the timings atwhich the two image pickup units start respective exposures, as well asto synchronize the timings at which the two image pickup units outputrespective image signals.

For the image pickup apparatuses 100 and 200, if the two image pickupunits (the first image pickup unit 110 and the second image pickup unit150) have the same exposure-output time (ΔA, ΔB), it is possible tosynchronize the timings at which the two image pickup units startexposures, as well as to synchronize the timings at which the two imagepickup units output image signals. However, if the exposure-output timevaries between the two image pickup units, it is not possible to obtaina correct three-dimensional picture by only synchronizing the timings atwhich the two image pickup units start exposures.

On the other hand, even when the exposure-output time varies between thetwo image pickup units (the first image pickup unit 110 and a secondimage pickup unit 250), an image pickup apparatus 300 shown in FIG. 6can synchronize the timings at which the two image pickup units startexposures, as well as can synchronize the timings at which the two imagepickup units output image signals. A specific example in which theexposure-output time AA of the first image pickup unit 110 is shorterthan the exposure-output time AB of the second image pickup unit 250will be described.

As shown in FIG. 6, the image pickup apparatus 300 according to thethird embodiment of the present invention includes the first imagepickup unit 110, the second image pickup unit 250, a delay unit 280, andthe display unit 190.

The image pickup apparatus 300 is similar to the image pickup apparatus200 according to the second embodiment except that the delay unit 280 isprovided between the first image pickup unit 110 and the display unit190, that the exposure-output time AA of the first image pickup unit 110is shorter than the exposure-output time AB of the second image pickupunit 250, and that the analysis unit 270 further includes a secondcontrol unit 274.

Hereafter, the delay unit 280, and the second control unit 274 includedin the analysis unit 270 of the second image pickup unit 250 will bedescribed. The other function blocks are similar to the correspondingfunction blocks of the image pickup apparatus 200 and therefore will notbe described.

The delay unit 280 delays an image signal and a synchronization signalfrom the first image pickup unit 110 by the amount of delay indicated bya second control signal CTR2 from the second image pickup unit 250.Accordingly, if the amount of delay indicated by the second controlsignal CTR2 is “0,” the image signal and the synchronization signaloutputted by the first image pickup unit 110 are similar to an imagesignal and a synchronization signal outputted to the display unit 190 bythe delay unit 280.

First, referring to FIG. 7, there will be described the timings of thesignals in a case in which the first control unit 176 does not controlthe timing at which the first image pickup unit 110 starts an exposureand in which the second control unit 274 does not control the delay unit280. Then, the second control unit 274 will be described. In this case,the respective values indicated by the first control signal CTR1 and thesecond control signal CTR2 are always “0.”

FIG. 7 corresponds to FIG. 2, which is referred to when describing thefirst and second embodiments. As shown in FIG. 7, the respective timingsat which the first image pickup unit 110 and the second image pickupunit 250 start exposures are not synchronized. The respective timings atwhich the delay unit 280 and the second image pickup unit 250 outputimage signals to the display unit 190 are not synchronized, either.Further, the exposure-output time ΔB of the second image pickup unit 250is longer than the exposure-output time ΔA of the first image pickupunit 110.

FIG. 8 corresponds to FIG. 5, which is referred to when describing thesecond embodiment, and is a diagram showing the timings of the signalsin a case in which the first control unit 176 controls the timing atwhich the first image pickup unit 110 starts an exposure and in whichthe second control unit 274 does not control the delay unit 280 (thesecond control signal CTR2 is always “0”).

In this case, due to the first control signal CTR1 outputted by thefirst control unit 176 and indicating the difference Δt2, the starttimings of the third and later exposures (third, fourth, etc.) by thefirst image pickup unit 110 are the same as the start timings of thethird and later exposures (third, fourth, etc.) by the second imagepickup unit 150, respectively.

However, the exposure-output time AA of the first image pickup unit 110is shorter than the exposure-output time AB of the second image pickupunit 250. Accordingly, even if the timings at which the first imagepickup unit 110 starts the exposures are the same as the timings atwhich the second image pickup unit 250 starts the exposures, the timingsat which the first image pickup unit 110 outputs image signals to thedisplay unit 190 via the delay unit 280 after performing the exposuresare earlier than the timings at which the second image pickup unit 250outputs image signals obtained by starting the exposures at the sametimings, to the display unit 190, respectively. The difference betweenthese output timings is represented by a third difference Δt3 in FIG. 8.

In the image taking apparatus 300, the second control unit 274 of theanalysis unit 270 calculates the third difference Δt3 after the firstcontrol unit 176 adjusts the exposure start timing. Specifically, basedon the synchronization signal SA, the second control unit 274 calculatesthe difference between the timing at which the first image pickup unit110 starts outputting a predetermined image signal and the timing atwhich the second image pickup unit 250 starts outputting an image signalimmediately after the first image pickup unit 110 starts outputting thepredetermined image signal. The second control unit 274 then outputs, tothe delay unit 280, the second control signal CTR2 indicating the amountof delay corresponding to this difference, that is, the third differenceΔt3.

The “predetermined image signal” whose output timing the second controlunit 274 uses in the calculation of the third difference Δt3 may be anyof image signals obtained by the first image pickup unit 110 throughexposures after the first control unit 176 adjusts the exposure starttiming. However, to synchronize the output timings earlier, a preferredpredetermined image signal is an image signal obtained through anearlier exposure.

In the example shown in FIG. 8, the earliest exposure performed by thefirst image pickup unit 110 after the first control unit 176 adjusts thetiming at which the first image pickup unit 110 starts an exposure isthe third exposure after the first image pickup unit 110 receives theexposure start signal ST. The image signal that the second image pickupunit 250 starts outputting immediately after the first image pickup unit110 starts outputting an image signal obtained through the aboveexposure is an image signal obtained through the third exposureperformed by the second image pickup unit 250.

Accordingly, the second control unit 274 calculates, as the thirddifference Δt3, the difference between the timing at which the firstimage pickup unit 110 starts outputting the image signal obtainedthrough the third exposure thereof and the timing at which the secondimage pickup unit 250 starts outputting the image signal obtainedthrough the third exposure thereof. The second control unit 274 thenoutputs the second control signal CTR2 indicating the third differenceΔt3 to the delay unit 280.

When the delay unit 280 receives the second control signal CTR2, itdelays the timing at which the output of an image signal (an imagesignal obtained through the fourth exposure) to be outputted to thedisplay unit 190 next is started, by the third difference Δt3. Thus, thetimings of the signals become those as shown in FIG. 9.

As shown in FIG. 9, the first image pickup unit 110 delays the timing atwhich it starts outputting an image signal obtained through the fourthexposure thereof to the display unit 190, by the third difference Δt3.As a result, starting with this image signal, respective image signalsobtained through exposures performed by the first image pickup unit 110and the second image pickup unit 250 are synchronized and inputted tothe display unit 190.

As seen above, even when the exposure-output time varies between thefirst image pickup unit 110 and the second image pickup unit 250, theimage pickup apparatus 300 according to the present embodiment cansynchronize the timings at which the two image pickup units startexposures, as well as can synchronize the timings at which the two imagepickup units output image signals.

The present invention has been described based on the embodiments. Theembodiments are only illustrative, and various changes, additions, ordeletions may be made thereto without departing from the spirit of thepresent invention. It will be appreciated by those skilled in the artthat any modifications resulting from a change, addition, or deletionfall within the scope of the invention.

For example, while the image pickup apparatuses including two imagepickup units have been described as the embodiments, the presentinvention is also applicable to image pickup apparatuses including morethan two image pickup units, as a matter of course.

In the image taking apparatus 300 according to the third embodiment, thedelay unit 280 is provided outside the image pickup unit having theshorter exposure-output time (first image pickup unit 110).Alternatively, a function block serving as the delay unit 280 may beprovided in the image pickup unit having the shorter exposure-outputtime if the image pickup unit can accommodate such a function block, orthe function of the delay unit 280 may be added to an existing functionblock (for example, analysis unit 130) of the image pickup unit.

While the image pickup apparatus 300 uses the method used by the imagepickup apparatus 200 according to the second embodiment as the methodfor adjusting the timings at which the first image pickup unit 110 andthe second image pickup unit 250 start exposures, it may use the methodused by the image pickup apparatus 100 according to the firstembodiment.

While the exposure start timing and the image signal output timing areeach adjusted only once in the embodiments, these timings may beadjusted a plurality of times. Where these adjustments are made aplurality of times, they may be made at predetermined intervals.

The present application claims priority based on Japanese UnexaminedPatent Application No. 2011-050114, filed on Mar. 8, 2011, thedisclosure of which is incorporated herein in its entirety.

REFERENCE SIGNS LIST

-   12 FIRST CCD IMAGE PICKUP UNIT-   14 FIRST CDS/AGC/AD UNIT-   22 SECOND CCD IMAGE PICKUP UNIT-   24 SECOND CDS/AGC/AD UNIT-   34 SENSOR DRIVE SIGNAL GENERATION UNIT-   100 IMAGE PICKUP APPARATUS-   110 FIRST IMAGE PICKUP UNIT-   120 IMAGE SENSOR MODULE-   122 LENS-   124 IMAGING ELEMENT-   126 ADJUSTMENT UNIT-   130 ANALYSIS UNIT-   132 ANALYSIS UNIT-   150 SECOND IMAGE PICKUP UNIT-   160 IMAGE SENSOR MODULE-   162 LENS-   164 IMAGING ELEMENT-   166 ADJUSTMENT UNIT-   170 ANALYSIS UNIT-   172 FIRST CONTROL UNIT-   174 ANALYSIS UNIT-   176 FIRST CONTROL UNIT-   190 DISPLAY UNIT-   200 IMAGE PICKUP APPARATUS-   250 SECOND IMAGE PICKUP UNIT-   270 ANALYSIS UNIT-   274 SECOND CONTROL UNIT-   280 DELAY UNIT-   300 IMAGE PICKUP APPARATUS-   T EXPOSURE INTERVAL-   Δt1 FIRST DIFFERENCE-   Δt2 SECOND DIFFERENCE-   Δt3 THIRD DIFFERENCE-   CTR1 FIRST CONTROL SIGNAL-   CTR2 SECOND CONTROL SIGNAL

1. A camera comprising: a first image pickup unit that repeats anexposure and output of an image signal obtained through the exposure toobtain a first picture signal and outputs the first picture signal; asecond image pickup unit that repeats an exposure and output of an imagesignal obtained through the exposure to obtain a second picture signaland outputs the second picture signal; and a first control unit thatcontrols the timing at which the first image pickup unit or the secondimage pickup unit starts an exposure, a display unit that generates athree-dimensional picture using the first picture signal outputted fromthe first image pickup unit and the second picture signal outputted fromthe second image pickup unit, and displays the three-dimensionalpicture, wherein the first control unit subtracts a first differencefrom an exposure-output time of the first image pickup unit to obtain asecond difference, and outputs a first control signal, the first controlsignal delaying one of i) the timing at which the second image pickupunit starts an exposure, by a value obtained by subtracting the seconddifference from an exposure interval, and ii) the timing at which thefirst image pickup unit starts an exposure, by the second difference,the exposure-output time being a time lag between when each of the firstand second image pickup units starts an exposure and when the imagepickup unit starts outputting an image signal obtained through theexposure, the first difference being a difference between the timingwhen the first image pickup unit started outputting a predeterminedimage signal and the timing when the second image pickup unit started anexposure for obtaining an image signal that the second image pickup unitoutputted immediately after the first image pickup unit startedoutputting the predetermined image signal.
 2. The camera according toclaim 1, wherein the first control unit obtains the timing at which thefirst image pickup unit started outputting the predetermined imagesignal, on the basis of a first synchronization signal insynchronization with which the first image pickup unit outputs an imagesignal.
 3. The camera according to claim 2, wherein the first controlunit is disposed on the same chip as a chip on which the second imagepickup unit is disposed.
 4. The camera according to claim 3, wherein thefirst control unit is disposed on the same chip as a chip on which thesecond image pickup unit is disposed.
 5. The camera according to claim1, further comprising a second control unit that controls the timingwhen one image pickup unit, which is the first or second image pickupunit having the shorter exposure-output time, outputs an image signalincluded in a picture signal, wherein the second control unit calculatesa third difference, the third difference being a difference between thetiming at which the one image pickup unit started outputting apredetermined image signal included in the picture signal and the timingat which the other image pickup unit started outputting an image signal,included in an picture signal, immediately after the predetermined imagesignal, and outputs a second control signal for delaying the timing atwhich the one image pickup unit starts outputting an image signalsubsequent to the predetermined image signal included in the picturesignal, by the third difference.
 6. The camera according to claim 2,further comprising a second control unit that controls the timing whenone image pickup unit, which is the first or second image pickup unithaving the shorter exposure-output time outputs an image signal includedin a picture signal, wherein the second control unit calculates a thirddifference, the third difference being a difference between the timingat which the one image pickup unit started outputting a predeterminedimage signal included in the picture signal and the timing at which theother image pickup unit started outputting an image signal, included inan picture signal, immediately after the predetermined image signal, andoutputs a second control signal for delaying the timing at which the oneimage pickup unit starts outputting an image signal subsequent to thepredetermined image signal included in the picture signal, by the thirddifference.
 7. The camera according to claim 3, further comprising asecond control unit that controls the timing when one image pickup unit,which is the first or second image pickup unit having the shorterexposure-output time, outputs an image signal included in a picturesignal, wherein the second control unit calculates a third difference,the third difference being a difference between the timing at which theone image pickup unit started outputting a predetermined image signalincluded in the picture signal and the timing at which the other imagepickup unit started outputting an image signal, included in an picturesignal, immediately after the predetermined image signal, and outputs asecond control signal for delaying the timing at which the one imagepickup unit starts outputting an image signal subsequent to thepredetermined image signal included in the picture signal, by the thirddifference.
 8. The camera according to claim 4, further comprising asecond control unit that controls the timing when one image pickup unit,having the shorter exposure-output time, outputs an image signalincluded in a picture signal, wherein the second control unit calculatesa third difference, the third difference being a difference between thetiming at which the one image pickup unit started outputting apredetermined image signal included in the picture signal and the timingat which the other image pickup unit started outputting an image signal,included in an picture signal, immediately after the predetermined imagesignal, and outputs a second control signal for delaying the timing atwhich the one image pickup unit starts outputting an image signalsubsequent to the predetermined image signal included in the picturesignal, by the third difference.